So, following your logic, Katakuri may have speed, versatility, and other attributes above Kiku, but that doesn’t change the fact that he lacks the AP to deal any significant damage to Kaidou. If Kiku, who used Ryou, could only inflict a shallow wound, and if four Scabbards combining their attacks could only cause superficial damage to Kaidou, then Kiku was already in a terrible position here. What could Katakuri do without that level of Haki? At best, he could dodge and prolong the fight, but that doesn’t mean he has any real chance of victory. If Kiku managed to deal minor damage and was still irrelevant, then Katakuri, without comparable offensive Haki, is just a fighter who could survive longer but would never pose a real threat. In the end, the result would be the same: Katakuri doesn’t have the power to take down Kaidou and would be nothing more than a nuisance to him.
Overall, Katakuri is far superior to Kiku, but against Kaidou, the difference in their levels doesn't matter—neither of them poses a real threat on their own.